Pivotal bone anchor assembly having a deployable collet insert with internal pressure ring

ABSTRACT

A pivotal bone anchor assembly for securing an elongate rod to patient bone includes a shank having a head and an anchor portion, a receiver having an axial bore and a channel for receiving the elongate rod, a collet insert top loaded into a first position within the axial bore and having a collet pocket for receiving the shank head, and a pressure ring uploadable into the collet pocket prior to the shank head and having an upper surface for engaging the rod. After receiving the shank head within the collet pocket, the collet insert and pressure ring are downwardly deployable with the shank head into a second position to capture the shank head in the assembly, the pressure ring being operable to transfer pressure from the elongate rod in the channel to the shank head to lock an angular position of the shank relative to the receiver.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/686,122, filed Nov. 16, 2019, which claims the benefit of U.S.Provisional Application No. 62/768,732, filed Nov. 16, 2018, and U.S.Provisional Application No. 62/811,250, filed Feb. 27, 2019, each ofwhich is incorporated by reference in its entirety herein, and for allpurposes.

FIELD OF THE INVENTION

The present invention generally relates to pivotal bone anchorassemblies for use in bone surgery, particularly spinal surgery.

BACKGROUND

Bone screws are utilized in many types of spinal surgery in order tosecure various implants to vertebrae along the spinal column for thepurpose of stabilizing and/or adjusting spinal alignment. Although bothclosed-ended and open-ended bone screws are known, open-ended screws areparticularly well suited for connections to rods and connector arms,because such rods or arms do not need to be passed through a closedbore, but rather can be laid or urged into an open channel within areceiver or head of such a screw.

Typical open-ended bone screws include a threaded shank with a pair ofparallel projecting branches or arms which form a yoke defining slot orchannel having different shapes, such as U-shaped and square shaped, forexample, to receive a rod. Hooks and other types of connectors, as areused in spinal fixation techniques, may also include open ends forreceiving rods or portions of other structure.

A common mechanism for providing vertebral support is to implant bonescrews into certain bones which then in turn support a longitudinalstructure such as an elongate rod, or are supported by such a rod. Bonescrews of this type may have a fixed head or receiver relative to ashank thereof. In the fixed bone screws, the rod receiver head cannot bemoved relative to the shank and the rod must be favorably positioned inorder for it to be placed within the receiver head. This is sometimesvery difficult or impossible to do. Therefore, pivotal or polyaxial bonescrews are commonly preferred. Open-ended polyaxial bone screwstypically allow for pivoting and rotation of the separate receiver aboutthe shank in one or more planes until a desired rotational position ofthe receiver is achieved by fixing such position relative to the shankduring a final stage of a medical procedure when an elongate rod orother longitudinal connecting member is inserted into the receiver,followed by a locking set screw or other closure.

SUMMARY

Briefly described, one embodiment of the present disclosure comprises apivotal bone anchor assembly for securing an elongate rod to patientbone. The pivotal bone anchor system generally includes a shank having ahead and an anchor portion, a receiver having an axial bore and an openchannel for receiving the elongate rod, and a collet insert that is toploadable into a first upper position within the axial bore of thereceiver. The collet insert includes a lower collet-type chamber orpocket for receiving the shank head. The bone anchor assembly alsoincludes a pressure ring that is uploadable into the collet pocket priorto the shank head, and having an upper surface for engaging the elongaterod. After receiving the shank head within the collet pocket below thepressure ring, the collet insert and pressure ring are downwardlydeployable together with the shank head into a second position withinthe axial bore to capture the shank head within the bone anchorassembly. With the collet insert in the second position, the pressurering is operable to transfer an applied pressure from the elongate rodpositioned in the open channel to the shank head to lock an angularposition of the shank relative to the receiver.

The invention will be better understood upon review of the detaileddescription set forth below taken in conjunction with the accompanyingdrawing figures, which are briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a pivotal bone anchorassembly, in accordance with a representative embodiment of the presentdisclosure.

FIG. 2 is an exploded perspective view of the bone anchor of the pivotalbone anchor assembly of FIG. 1.

FIG. 3 is a cross-sectional perspective view of the shank head of thebone anchor of FIG. 2.

FIG. 4. is a perspective of the receiver of the pivotal bone anchorassembly of FIG.

FIG. 5 is a cross-sectional side view of the receiver of FIG. 4.

FIG. 6 is a cross-sectional perspective view of the receiver of FIG. 4.

FIG. 7 is another cross-sectional perspective view of the receiver ofFIG. 4.

FIG. 8 is a perspective view of the collet insert of the pivotal boneanchor assembly of FIG. 1.

FIG. 9 is a cross-sectional perspective view of the collet insert ofFIG. 8.

FIG. 10 is a cross-sectional side view of the collet insert of FIG. 8.

FIG. 11 is a top view of the collet insert of FIG. 8.

FIG. 12 is a bottom view of the collet insert of FIG. 8.

FIG. 13 is a perspective view of the internal pressure ring of thepivotal bone anchor assembly of FIG. 1.

FIG. 14 is a cross-sectional perspective view of the internal pressurering of FIG. 13.

FIG. 15 is a side view of the closure of the pivotal bone anchorassembly of FIG.

FIG. 16 is an upper perspective view of the closure of FIG. 15.

FIG. 17 is a lower perspective view of the closure of FIG. 15.

FIG. 18 is a cross-sectional perspective view of the closure of FIG. 15.

FIG. 19 is an exploded perspective view of the receiver, collet insert,and internal pressure ring components of the receiver sub-assembly priorto their pre-assembly into a shipping state configuration.

FIG. 20 is a partially cut-away perspective view of the receiver of FIG.19 with the collet insert being installed therein.

FIG. 21 is a partially cut-away perspective view of the receiver of FIG.19 with the collet insert preassembled into its shipping state position.

FIG. 22 is a partially cut-away perspective view of the pre-assembledreceiver and collet insert of FIG. 21, with the internal pressure ringbeing installed therein.

FIG. 23 is a sectioned perspective view of the receiver, collet insert,and internal pressure ring of FIG. 22.

FIG. 24 is a partially cut-away perspective view of the receiversub-assembly, with the collet insert and internal pressure ringpre-assembled into their shipping state positions within the receiver.

FIG. 25 is a sectioned perspective view of the receiver sub-assembly ofFIG. 24.

FIG. 26 is a close-up sectioned perspective view of the upper end of thecollet insert in the pre-assembled configuration of FIG. 21.

FIG. 27 is a close-up sectioned perspective view of the upper end of thecollet insert and internal pressure ring in the pre-assembledconfiguration of FIGS. 24-25.

FIG. 28 is a close-up sectioned perspective view of the lower end of thecollet insert in the pre-assembled configuration of FIGS. 21-25.

FIG. 29 is a partially cut-away perspective view of the receiversub-assembly positioned above the shank head of a bone anchor.

FIG. 30 is a sectioned perspective view of the receiver sub-assembly andbone anchor of FIG. 29.

FIG. 31 is a sectioned perspective view of the receiver sub-assemblymoving downward until the shank head enters the bottom opening and theupper portion of the shank head spherical outer surface contacts theinnermost edges of the distal tip sections.

FIG. 32 is a partially cut-away perspective view of the receiversub-assembly moving further downward onto the shank head, causing thecollet fingers to flex outward and the distal pocket opening to expandwithin the upper expansion chamber portion of the receiver cavity untilthe distal pocket opening reaches maximum expansion.

FIG. 33 is a sectioned perspective view of the receiver sub-assembly andshank head of FIG. 32.

FIG. 34 is a partially cut-away perspective view of the receiversub-assembly moving further downward until the shank head reachesmaximum push through within the collet pocket and the upper portion ofthe shank head spherical outer surface abuts the concave bottom surfaceof the pressure ring.

FIG. 35 is a sectioned perspective view of the receiver sub-assembly andshank head of FIG. 34.

FIG. 36 is a partially cut-away perspective view of the receiversub-assembly moving back upward until the lower portion of the shankhead spherical outer surface contacts the plurality of inner partialspherical surfaces of the distal tip sections.

FIG. 37 is a sectioned perspective view of the receiver sub-assembly andshank head of FIG. 36.

FIG. 38 is a partially cut-away perspective view of the receiversub-assembly and coupled shank head, with the collet insert pusheddownwardly into a partially deployed position.

FIG. 39 is a sectioned perspective view of the receiver sub-assembly andshank head of FIG. 38.

FIG. 40 is a partially cut-away perspective view of the receiversub-assembly and coupled shank head, with the collet insert pushedfurther downwardly into a fully deployed position.

FIG. 41 is a sectioned perspective view of the receiver sub-assembly andshank head of FIG. 40.

FIG. 42 is a partially cut-away perspective view of the receiversub-assembly and coupled shank head, with the pressure ring pusheddownwardly from its position in the upper portion of the collet pocketuntil the concave partial spherical bottom surface of the pressure ringengages the upper portion of the shank head spherical surface.

FIG. 43 is a sectioned perspective view of the receiver sub-assembly andshank head of FIG. 42.

FIG. 44 is a partially cut-away perspective view of the receiversub-assembly and coupled shank head, and further with an elongate rodand closure, in a fully locked configuration.

FIG. 45 is a sectioned perspective view of the receiver sub-assembly,shank head, elongate rod, and closure in the fully locked configurationof FIG. 44.

FIG. 46 is a close-up partially cut-away perspective view of the lowerend of the collet insert, shank head, and pressure ring in the fullylocked configuration of FIG. 44.

FIG. 47 is a sectioned side view of the receiver sub-assembly, shankhead, elongate rod, and closure in the fully locked configuration ofFIG. 44, with the bone anchor being pivoted relative to the receiver.

FIG. 48 is another sectioned side view, orthogonal to FIG. 47, of thereceiver sub-assembly, shank head, elongate rod, and closure in thefully locked configuration of FIG. 44, with the bone anchor beingpivoted relative to the receiver.

FIG. 49 is a perspective view of the receiver sub-assembly and shankhead after removal of the closure and elongate rod and remobilization ofthe receiver sub-assembly.

FIG. 50 is another perspective view of the receiver sub-assembly andshank head of FIG. 49, with the receiver sub-assembly being pivotedrelative to the shank head.

FIG. 51 is close-up sectioned perspective view of the receiversub-assembly and shank head of FIG. 50.

FIG. 52 is a perspective view of the receiver sub-assembly and shankhead after insertion of a disassembly tool into engagement with theupper tool engagement recesses of the collet insert.

FIG. 53 is sectioned perspective view of the receiver sub-assembly,shank head, and disassembly tool of FIG. 52.

FIG. 54 is close-up sectioned perspective view of the receiversub-assembly, shank head, and disassembly tool of FIG. 53.

FIG. 55 is sectioned perspective view of the receiver sub-assembly,shank head, and disassembly tool after the withdrawal of the colletinsert back up to the upper shipping state configuration.

FIG. 56 is close-up sectioned perspective view of the receiversub-assembly, shank head, and disassembly tool of FIG. 55.

FIG. 57 is sectioned perspective view of the receiver sub-assembly,shank head, and disassembly tool with the receiver sub-assembly beingpartially removed from the shank head.

FIG. 58 is close-up sectioned perspective view of the receiversub-assembly, shank head, and disassembly tool of FIG. 57.

FIG. 59 is sectioned perspective view of the receiver sub-assembly,shank head, and disassembly tool with the receiver sub-assembly beingentirely removed from the shank head.

FIG. 60 is a partially cut-away perspective view of a receiversub-assembly, shank head, elongate rod, and closure in the fully lockedconfiguration, in accordance with another representative embodiment ofthe present disclosure.

FIG. 61 is a cross-sectional perspective view of the receiver of FIG.60.

FIG. 62 is a perspective view of the collet insert of FIG. 60.

FIG. 63 is a close-up partially cut-away side view of the receiversub-assembly, shank head, and elongate rod of FIG. 60.

FIG. 64 is a partially cut-away perspective view of a receiversub-assembly, shank head, elongate rod, and closure in the fully lockedconfiguration, in accordance with yet another representative embodimentof the present disclosure.

FIG. 65 is a cross-sectional perspective view of the receiver of FIG.64.

FIG. 66 is a perspective view of the collet insert of FIG. 64.

FIG. 67 is a close-up partially cut-away side view of the receiversub-assembly, shank head, and elongate rod of FIG. 64.

FIG. 68 is a partially cut-away perspective view of a receiversub-assembly, including an expansion ring, during assembly with a shankhead, in accordance with yet another representative embodiment of thepresent disclosure.

FIG. 69 is a cross-sectional perspective view of the receiver of FIG.68.

FIG. 70 is a perspective view of the collet insert of FIG. 68.

FIG. 71 is a perspective view of the expansion ring of FIG. 68.

FIG. 72 is a partially cut-away perspective view of the receiversub-assembly and shank head of FIG. 68, together with an elongate rodand closure, in the fully locked configuration.

FIG. 73 is a sectioned perspective view of the receiver sub-assembly,shank head, elongate rod, and closure in the fully locked configurationof FIG. 72.

FIG. 74 is a cross-sectional side view of the receiver sub-assembly andshank head in the fully locked configuration of FIG. 72.

FIG. 75 is a partially cut-away perspective view of a receiversub-assembly, including an expansion ring, during assembly with a shankhead, in accordance with yet another representative embodiment of thepresent disclosure.

FIG. 76 is a cross-sectional perspective view of the receiver of FIG.75.

FIG. 77 is a perspective view of the collet insert of FIG. 75.

FIG. 78 is a perspective view of the expansion ring of FIG. 75.

FIG. 79 is a partially cut-away perspective view of the receiversub-assembly and shank head of FIG. 75, together with an elongate rodand closure, in the fully locked configuration.

FIG. 80 is a sectioned perspective view of the receiver sub-assembly,shank head, elongate rod, and closure in the fully locked configurationof FIG. 79.

FIG. 81 is a cross-sectional side view of the receiver sub-assembly andshank head in the fully locked configuration of FIG. 79.

FIG. 82 is a perspective view of a pair of pivotal bone anchorassemblies coupled to shank heads, each with housings configured foradjacent level connection, in accordance with yet another representativeembodiment of the present disclosure.

FIG. 83 is a partially cut-away perspective view of one of the pair ofpivotal bone anchor assemblies and its coupled shank head of FIG. 82.

FIG. 84 is an isolated perspective view of the pivotal bone anchorassembly and bone anchor of FIG. 83 upon removal of the housing.

Those skilled in the art will appreciate and understand that, accordingto common practice, various features and elements of the drawingsdescribed above are not necessarily drawn to scale, and that thedimensions and relative positions between the features or elements maybe expanded, reduced or otherwise altered to more clearly illustrate thevarious embodiments of the present disclosure depicted therein.

DETAILED DESCRIPTION

The following description, in conjunction with the accompanying drawingsdescribed above, is provided as an enabling teaching of exemplaryembodiments of a pivotal bone anchor apparatus or assembly, togetherwith methods for assembling and using the pivotal bone anchor apparatusor assembly. As described below, the apparatuses, assemblies, and/ormethods of the present disclosure can provide several significantadvantages and benefits over other pivotal bone anchors known in theart. However, the recited advantages are not meant to be limiting in anyway, as one skilled in the art will appreciate that other advantages mayalso be realized upon practicing the present disclosure.

Furthermore, those skilled in the relevant art will recognize thatchanges can be made to the described embodiments while still obtainingthe beneficial results. It will also be apparent that some of theadvantages and benefits of the described embodiments can be obtained byselecting some of the features of the embodiments without utilizingother features, and that features from one embodiment may beinterchanged or combined with features from other embodiments in anyappropriate combination. For example, any individual or collectivefeatures of method embodiments may be applied to apparatus, product orsystem embodiments, and vice versa. Accordingly, those who work in theart will recognize that many modifications and adaptations to theembodiments described are possible and may even be desirable in certaincircumstances, and are a part of the disclosure. Thus, the presentdisclosure is provided as an illustration of the principles of theembodiments and not in limitation thereof, since the scope of theinvention is to be defined by the claims.

Referring now in more detail to the drawing figures, wherein like partsare identified with like reference numerals throughout the severalviews, FIG. 1 illustrates a representative embodiment of a pivotal boneanchor apparatus or assembly 10 (hereinafter referenced to as “theassembly 10”) for securing an elongate rod to patient bone in spinalsurgery. The assembly 10 generally includes a bone anchor, such as shank20, having a capture portion, such as shank head 22, at a proximal end23, and an anchor portion or shank body 40 extending distally from theshank head 22 for securement to patient bone. The assembly alsogenerally includes a receiver 100 having an internal cavity 126 in abase portion 134 and two upright arms 104 extending upwardly from thebase portion to define a rod channel 106 for receiving an elongate rod70. The receiver 100 can be initially pivotably secured to the shankhead 22 with a number of separate internal components that have beenpre-assembled into the internal cavity 126 and the rod channel 106 toform a receiver sub-assembly 14. These components generally include acollet insert 150 and a pressure ring 190. After an elongate rod 70 hasbeen positioned within a lower portion of the rod channel 106, a closure50 can be threadably or otherwise secured into an upper portion of therod channel 106 to apply pressure to an upper surface of the elongaterod 70, which in turn applies pressure to the upper surface of thepressure ring 190, thereby locking both the elongate rod 70 and thepivotal bone anchor assembly 10 into a final locked position. Asdiscussed in more detail below, the shank head 22 is configured toprovide a multi-planar pivotable connection between the shank 20 and thereceiver sub-assembly 14 prior to fixing the shank 20 in a desiredposition with respect to the receiver sub-assembly 14.

With reference to FIGS. 2-3, the bone anchor or shank 20 generallycomprises the capture portion or shank head 22 at a proximal end 23, andan anchor portion or shank body 40 extending distally from the shankhead 22 toward a tip 48 at a distal end 49. The shank 20 is elongate,with the shank body 40 having a helically wound bone implantable thread44 (single, dual, or multiple-lead thread form) extending from near aneck 42 located adjacent to the shank head 22, to a distal tip 48 of thebody 40 and extending radially outwardly therefrom. During use, theshank body 40 utilizing the thread 44 for gripping and advancement isimplanted into the vertebra (not shown) of a patient leading with thetip 48 and driven down into the vertebra with an installation or drivingtool (also not shown), so as to be implanted in the vertebra to near theneck 42 of the shank 20, as more fully described in the paragraphsbelow. The shank 20 has a longitudinal axis, or axis of rotation, thatis generally identified by the reference numeral 21.

The non-threaded neck 42 extends axially upward from the shank body 40.The neck 42 may be of the same or is typically of a slightly reducedradius as compared to an adjacent upper end of the shank body 40 wherethe thread 44 terminates, with the reduced radius providing forincreased angulation of the receiver sub-assembly 14 relative to theshank. In one aspect the threaded shank body 44 and the non-threadedneck 42 can together define an anchor portion of the shank 20.

Extending further axially upwardly and outwardly from the neck 42 is theshank head 22 that provides a connective or capture structure disposedat a distance from the shank body 40, and thus at a distance from thevertebra when the shank body 40 is implanted in such vertebra. The shankhead 22 of the pivotal bone anchor assembly 10 generally has a partialspherical shape defining a hemisphere plane 30 at a maximum widthperpendicular to the longitudinal axis, and a partial spherical outersurface 32 extending above and below the hemisphere plane. As shown inthe drawings, the partial spherical outer surface 32 may have a singlecommon radius as it extends above the hemisphere plane 30 to an annularplanar top surface 24 and an internal driving tool engagement structure26 formed into the top of the shank head 22, and as it extends below thehemisphere plane 30 to the neck 42. It is foreseen, however, that othershapes and/or configurations for the shank head 22 are also possible andconsidered to fall within the scope of the present disclosure.

Located adjacent to the partial spherical outer surface 28 is an annularplanar top surface 24 that surrounds an internal drive feature 26 ordrive socket. The illustrated internal drive feature 26 is an apertureformed in the top surface 24, and in one aspect can be a multi-lobularor star-shaped aperture, such as those sold under the trademark TORX, orthe like, having internal faces 28 designed to receive a multi-lobularor star-shaped tool for rotating and driving the shank body 40. It isforeseen that such an internal tool engagement structure 26 may take avariety of tool-engaging forms and may include one or more apertures ofvarious shapes, such as a pair of spaced apart apertures or a hex shapedesigned to receive a hex tool (not shown) of an Allen wrench type. Theseat or base surface 27 of the drive feature 26 can be disposedperpendicular to the shank axis 21, with the drive feature 26 otherwisebeing coaxial with the axis 21. In operation, a driving tool is receivedin the internal drive feature 26, being seated at the base surface 27and engaging the internal faces 28 of the drive feature 26 for bothdriving and rotating the shank body 40 into the vertebra, either beforeor after the shank 20 is attached to the receiver sub-assembly 14, withthe shank body 40 being driven into the vertebra with the driving toolextending into the receiver 100.

In one aspect the shank 20 can be cannulated, with a bore 46 extendingthrough the entire length thereof, and centered about the longitudinalaxis 21 of the shank 20. The bore 46 is defined by an inner cylindricalwall 47 of the shank 20 and has a circular opening at the shank tip 48and an upper opening communicating with the internal drive 26 at theseat surface 27. The bore 46 is coaxial with the threaded shank body 40and the shank head 22. The bore 46 provides a passage through the shank20 interior for a length of wire (not shown) inserted into the vertebraprior to the collet insertion of the shank body 40, the wire providing aguide for insertion of the shank body 40 into the vertebra. The bore canalso provide for a pin to extend therethrough and beyond the shank tip,the pin being associated with a tool to facilitate insertion of theshank body into the vertebra.

To provide a biologically active interface with the bone, the threadedshank body 40 may be coated, perforated, made porous or otherwisetreated. The treatment may include, but is not limited to a plasma spraycoating or other type of coating of a metal or, for example, a calciumphosphate; or a roughening, perforation or indentation in the shanksurface, such as by sputtering, sand blasting or acid etching, thatallows for bony ingrowth or ongrowth. Certain metal coatings act as ascaffold for bone ingrowth. Bio-ceramic calcium phosphate coatingsinclude, but are not limited to: alpha-tri-calcium phosphate andbeta-tri-calcium phosphate (Ca₃(PO₄)₂, tetra-calcium phosphate(Ca₄P₂O₉), amorphous calcium phosphate and hydroxyapatite(Ca₁₀(PO₉)₆(OH)₂). Coating with hydroxyapatite, for example, isdesirable as hydroxyapatite is chemically similar to bone with respectto mineral content and has been identified as being bioactive and thusnot only supportive of bone ingrowth, but actively taking part in bonebonding.

Illustrated in FIGS. 4-7 is the receiver 100 of the pivotal bone anchorassembly 10 having a generally U-shaped appearance with a partiallydiscontinuous substantially cylindrical inner profile and apartially-cylindrical and partially-faceted outer profile, althoughother profiles are contemplated. The receiver 100 also has alongitudinal axis 101, or axis of rotation, that is shown in FIG. 1 asbeing aligned with the longitudinal axis 21 of the shank 20, suchorientation being desirable, but not required during assembly of thereceiver 100 with the shank 20. After the receiver 100 is pivotallyattached to the shank head 22, either before or after the shank 20 isimplanted in a vertebra, the receiver axis 101 is typically disposed atan angle with respect to the shank axis 21 as shown, for example, inFIGS. 47-48.

The receiver 100 includes a substantially cylindrical base 134 integralwith a pair of opposed upright arms 104 forming an upwardly open channel106 between the arms 104 for receiving the elongate rod 70. Each of thereceiver arms 104 has an interior face 110 that includes a discontinuousupper portion of a generally cylindrical axial or central bore 114 thatextends from the top surfaces 102 of the upright arms 104 at theproximal end 103 of the receiver 100, downwardly through the openchannel 106 and the base 134 to a bottom opening 136 at the distal end139 of the receiver 100. The channel portion or upper discontinuousportion of the central bore 114 is bounded on either side by opposingparallel planar surfaces 112 that curve downwardly into U-shaped lowersaddle surfaces 113, with the upper opposing planar surfaces 112 andlower saddle surface 113 defining the front and back ends of theupwardly open U-shaped channel 106. In one aspect of the presentdisclosure the receiver can include breakoff extensions (not shown)extending upwardly from the top surfaces 102 of the upright arms 104,and which can be threaded for threadable engagement with the outerthreads of the closure 50 (FIGS. 15-18).

The upper discontinuous portion of the cylindrical central bore 114further includes a partial helically wound guide and advancementstructure 116 extending radially inwardly from the interior face 110 ofthe channel 106 and located adjacent the top surfaces 102 of the arms104. In the illustrated embodiment, the guide and advancement structure116 is a partial helically wound interlocking flangeform configured tomate under rotation with a similar structure on the closure 50 (FIGS.15-18), as described more fully below. However, it is foreseen that theguide and advancement structure 116 could alternatively be asquare-shaped thread, a buttress thread, a modified buttress thread, areverse angle thread or other thread-like or non-thread-like helicallywound discontinuous advancement structure for operably guiding underrotation and advancing the closure 50 downward between the arms 104, aswell as eventual torqueing when the closure 50 abuts against theelongate rod 70. Additionally, the various structures and surfacesforming the guide and advancement structure 116 can be configured toresist, to inhibit, to limit, or to preferentially control the splay ofthe upright arms 104 under the rotation and advancing the closure 50downward between the arms 104.

The upper discontinuous portion of the cylindrical central bore 114immediately below the guide and advancement structure 116 is defined bya discontinuous cylindrical surface 118 that extends downward from theguide and advancement structure 116 to a expansion chamber portion 128of the receiver cavity 126. Formed into the discontinuous cylindricalsurface 118 is an upper “shipping state” groove 120 spaced below theguide and advancement structure 116, and a lower “capture/locking state”groove 122 located between the upper groove 120 and the receiver cavity126. In one aspect the upper groove 120 may be deeper and wider than thelower groove 122.

Communicating with and located beneath the channel 106 of the receiver100 at the base portion 134 thereof is the cavity 126 having an upperexpansion chamber portion 128 and a lower seating surface portion 132located proximate the bottom opening 136. The expansion chamber 128 isgenerally defined by an upper discontinuous downwardly-facing annularstep surface 125 demarking the bottom of the discontinuous cylindricalsurface 118, a lower transition surface 130, and a substantiallycylindrical sidewall surface 127 extending between the upper stepsurface 125 or the U-shaped saddle surfaces 113 of the channel 106 andthe lower transition surface 130. The diameter of the cylindricalsidewall surface 127 is generally greater than the diameter of thediscontinuous cylindrical surface 118 immediately above the upperexpansion chamber portion 128. Furthermore, the lower transition surface130 may have a downwardly and inwardly tapered, or frusto-conical,profile, or an inwardly curved profile, or similar. The lower transitionsurface 130 is generally not intended to be engaged by the collet insertduring assembly and use, and serves primarily as a transition structurebetween the upper expansion chamber portion 128 and the partialspherical interior seating surface 132 while providing material strengthfor supporting the partial spherical interior seating surface 132relative to the upper portion of the receiver base 134.

The lower seating surface portion 132 of the cavity 126 is spaced belowthe expansion chamber 128 by the frusto-conical transition surface 13,and can be a continuous partial spherical seating surface extending 360degrees around the lower circumference of the receiver cavity 126. Asdescribed in detail below, the partial spherical seating surface 132 ofthe receiver 100 is configured for frictional engagement with aplurality of outer partial spherical surfaces of the distal tip sections170 of a collet insert 150 (FIGS. 8-12) when a downwardly directedpressure is applied to a shank head that is captured within the colletinsert 150, as well as for releasing the engagement with the distal tipsections 170 when the pressure is removed.

Immediately below the seating surface 132 is a lowermost cylindricalsurface 135 that generally defines the bottom opening 136 thatcommunicates with both the internal cavity 126 and a receiver lowerexterior or bottom 138 of the base 134. The cylindrical surface 135 issubstantially coaxially aligned with respect to the longitudinal axis101 of the receiver 100, and is also sized and shaped to be smaller thanthe distal tip sections of the collet insert 150 when the shank head 22is captured within the collet insert 150, so as to form a restriction toprevent the shank head 22 from passing downward through the cavity 126and out the bottom opening 136 of the receiver 100 during the use of thepivotal bone anchor assembly.

As noted above, the outer surface 108 of the receiver 100 can have apartially-cylindrical and partially-faceted outer profile. In theembodiment of the receiver 100 illustrated in FIGS. 3-7, the faceted orplanar portions can include front and back outer planar faces 140 on thereceiver base 134 below the open channel 106 and extending upward alongthe side edges of the upright arms 104 to the top surfaces 102 of thearms. In addition, a pair of tool receiving and engaging recesses 142can be formed into the side outer faces 107 between each top surface 102and the receiver base 134, and can have recessed surfaces that areperpendicular with the front and back outer planar faces 140. In oneaspect additional front and back tool receiving and engaging recesses144 can be formed into the upper arm portions of the front and backouter planar faces 140. The faceted or planar portions 140 of the outersurface 108 of the receiver 100 and the tool receiving and engagingrecesses 142, 144 can serve together as outer tool engagement surfacesthat allow for tooling to securely engage and hold the receiver 100during an initial pre-assembly with the separate collet insert 150 andpressure ring 190 into the receiver 100 to form the receiversub-assembly 14, as well as during coupling of the receiver sub-assembly14 to the shank 20 after or before the implantation of the shank body 40into a vertebra, and during further assembly of the assembly 10 with theelongate rod 70 and the closure 50.

Although the rod channel 106 is shown as being an upwardly-open channelin the embodiment of the bone anchor receiver 100 shown in FIGS. 1 and4-7, it will be appreciated by one of skill in the art that in otherembodiments the receiver may be a closed top receiver, with the rodchannel becoming a rod aperture, and in which the elongate rod isintroduced into the receiver from the side rather than from the top.This feature may be especially useful when implanting a long series ofpivotal bone anchor assemblies along a patient's spine, and it isdetermined that it would be beneficial to use a closed top receiver atone end to better secure the elongate rod at the beginning of theseries.

It is foreseen, moreover, that other shapes and configurations for theinterior and exterior surfaces of the receiver 100, different from thoseshown in the drawings while providing for similar interaction andfunctionality of the various components of the pivotal bone anchorassembly, are also possible and considered to fall within the scope ofthe present disclosure. For example, the tool receiving and engagingrecesses 142, 144 may be replaced by horizontally-extending “top notch”type tool receiving grooves formed around the upper periphery of thereceiver arms 104, or additional planar faces formed into the side outersurfaces 107 of the receiver 100 (which may or may not be orthogonal tothe front and back outer planar faces 140 on the receiver base 134) arealso possible. Additional tool engaging structures or recesses can alsobe formed on the outer faces of breakoff extensions described above.

Illustrated in FIGS. 8-12 is the collet insert 150 having a lower,generally tubular collet portion 160 that defines an expandable internalchamber or collet pocket 164, with integral insert arms 154 projectingupwardly or proximally from the collet portion 160 to define an insertchannel 156 that is alignable with the receiver channel 106 uponinstallation of the collet insert 150 into the receiver 100. Theinterior surfaces of the insert arms 154 include opposed parallel planarsurfaces 151 that curve downwardly into U-shaped upper surfaces 182 ofopposed radial extensions 180 that project radially outward from thetubular collet portion 160 between the insert upright arms 154. Theopposed parallel planar surfaces 151 are located on either side of adiscontinuous upper cylindrical surface 153 formed into the interiorcenter portion of the insert arms 154 to define a central tool receivingaperture 169. The central tool receiving aperture 169 extends verticallydownward through the collet insert channel 156 and the upper end of thecollet portion 160 (and through the central aperture of the pressurering (FIGS. 13-14)) to allow passage for a driving tool to engage theinternal drive feature 24 or drive socket formed into the top of a shankhead 22 that is captured within the collet pocket 164. As illustrated inthe drawings, the central tool receiving aperture 169 can be smooth andnon-threaded.

The insert arms 154 have a width between the opposed parallel planarsurfaces 151 for operably snugly receiving the elongate rod 70.Furthermore, the insert arms 154 extend upwardly from the collet portion160 to top surfaces 152 that, in one aspect, are spaced below a topsurface of an elongate rod 70 when the rod is positioned in the insertand receiver channels 156, 106 (see FIGS. 44-45). The discontinuousupper cylindrical surface 153 of the insert arms 154 further includes aninternal tool engagement structure or recesses 155 formed therein thatare spaced below the top surfaces 152 of the insert arms 154. Forpurposes described in more detail below, the internal tool engagementstructure 155 is configured for engagement with tooling, such as anextraction tool or a deployment tool (not shown). Although shown as arecess 155 with smooth surfaces, in other embodiments the upper toolengagement structure could be threaded, with the tooling also beingthreaded at a distal end thereof

Protruding radially outwardly from the outer side surfaces 157 of theinsert arms 155 are opposed lateral ridges 158 that are configured for“snap-in” engagement with the upper grooves 120 and with the lowergrooves 122 formed into the interior faces 110 of the receiver uprightarms 104 when the receiver sub-assembly is in a pre-assembled shippingstate position or the capture/locking state position, respectively. Theprotruding lateral ridges are non-threaded, and in one aspect a smallrounded relief groove 159 can be formed at the junction between thevertical outer side surfaces 157 of the collet insert arms 152 and thetop surfaces of the opposed lateral ridges 158, for reasons described inmore detail below. It is foreseen that the arrangement of protrudingridges and recesses on the collet insert 150 and the receiver 100,respectively, can be reversed, with the shipping and locking recessesbeing formed into the exterior or outer surface of the collet insert 150and the internal ridges protruding inwardly from the receiver centralbore 114. Other combinations of ridges and grooves, or entirelydifferent structures, including but not limited to ratchets, a separatesnap ring, and the like, are also possible.

In the embodiment of the collet insert 150 illustrated in FIGS. 8-12,the opposed radial extensions 180 project radially outward from thetubular collet portion 160 between the insert upright arms 154 to endsurfaces 185, and can serve to perform a number of useful functions. Forexample, the radial extensions 180 can include substantially planar sideedge surfaces 186 that are configured to slidably engage with the upperopposing planar surfaces 112 of the receiver upright arms 104, so as toalign the open insert channel 156 with the open receiver channel 106.The radial extensions 180 can also include top edge surfaces 186 thatare substantially planar or flat, and which can be configured to atleast partially receive the deployment tooling (not shown) used to drivethe collet insert 150 downward within the receiver central bore 114during deployment from the pre-assembled shipping state position to thecapture/locking state position, as described below.

The upper surfaces 182 of the radial extensions 180 can also be curvedto match the underside of the elongate rod 70. However, it will beappreciated that the underside surfaces 92 of the elongate rod 70generally do not contact the upper surfaces 182 of the radial extensions180, in order to restrict or prevent the creation of an alternative loadpath from the elongate rod 70 down into the receiver body 100 other thanthe load path defined by the pressure ring 190. Thus, the upper surfaces182 of the radial extensions 180 may be shaped to match the curvature ofthe elongate rod so as to provide increased and uniform spacing betweenthe two curved surfaces, so as to better avoid accidental contact duringassembly and use.

Similarly, the lower or underside surfaces 188 of the radial extensions180 can also be curved to match with the curved saddle surfaces 113extending between the receiver upright arms 104, thereby allowing for anincreased range of vertical movement between the two surfaces.Generally, the curved underside surfaces 188 of the radial extensions180 are maintained in a position that is spaced above the curved saddlesurfaces 113, in order to restrict or prevent the creation of analternative load path between the collet insert 150 and the receiverbody 100 other than the load path defined by the opposed lateral ridges158 and the distal tips sections 170, as described in detail below.Alternatively, it is contemplated that the curved underside surfaces 188can be configured to engage with the curved saddle surface 113 as anindexing surface, so as to align the distal tip sections 170 with thepartial spherical seating surface 132 of the receiver cavity 126, and/orto provide additional support for the radial extensions 180.

As noted above, the collet portion 160 has a generally tubularconstruction with substantially cylindrical sidewalls 162 having innersurfaces 163 defining an expandable internal chamber or collet pocket164 for receiving and engaging both the pressure ring 190 and the shankhead 22. The proximal or upper portion of the collet pocket 164 isdefined by a discontinuous, downward-facing stop surface or shelfsurface 161 that extends radially outward below the discontinuous uppercylindrical surface 153, and which serves as the internal bottom surfaceof the upright insert arms 154. Moving downward from thedownwardly-facing stop surface 161, a plurality of longitudinal slots166 are formed through the sidewalls 162 of the collet portion 160 thatsub-divide the collet portion into a plurality of resilient colletfingers 168. The upper ends of the slots 166 can terminate in roundedstress-relieving apertures 167, including but not limited to circularand oval shapes. The resilient collet fingers 168 are configured tomaintain their downward orientation except when deflected outwardly bythe passage of the shank head 22 or pressure ring 190, as described indetail below.

Distal tip sections 170 curve inwardly at the lower ends of theresilient collet fingers 168 to partially close the distal end 179 ofthe expandable collet pocket 164 and to define an expandable distalpocket opening 176 that returns to its nominal shape after deflection bythe passage of the shank head 22 or pressure ring 190. The innerportions of the distal tip sections 170 define a plurality of innerpartial spherical surfaces 172 that engage the spherical outer surface32 of the shank head 22 below the hemisphere plane 30. The outerportions of the distal tip sections 170 define a plurality of outerpartial spherical surfaces 174 that are configured to engage the partialspherical interior seating surface 132 of the receiver cavity 126,generally without contraction or inward displacement of the colletfingers 168, when the collet insert 150 is in the capture/locking stateposition. Extending between the inner partial spherical surfaces 172 andthe bottom surfaces 178 of the distal tip sections 170 are chamferedsurfaces 175 that can engage the upper outer edge of the pressure ringor the spherical outer surface of the shank head to facilitate theuploading of the pressure ring and shank head, respectively, into theexpandable collet pocket 164. In addition, the junction between theinner partial spherical surfaces 172 and the chamfered surfaces 175 forma plurality of innermost edges 173 that together define the size of thedistal pocket opening 176. If desired, the innermost edges 173 andchamfered surface 173 can be rounded together to form rounded innermostedges that are continuously curved between the inner partial sphericalsurfaces 172 and the bottom surfaces 178 of the distal tip sections 170.

As can be seen in the drawings, the distal tip sections 170 can have athickness that is greater than the thickness of the tubular sidewalls162 of the collet portion 160, so that each of the distal tip sectionshas a bulbous profile. In one aspect the thickness of the distal tipsections 170 can be varied or controlled so as to better position theirouter partial spherical surfaces 174 relative to the partial sphericalinterior seating surface 132, as well as to provide increased metallicmaterial to support against pullout of the shank head 22 during assemblyand use.

It is foreseen that other shapes and configurations for the interior andexterior surfaces of the collet insert, different from those shown inthe drawings while providing for similar interaction and functionalityof the various components of the pivotal bone anchor assembly, are alsopossible and considered to fall within the scope of the presentdisclosure. For example, the collet insert can be positioned within thereceiver in different ways, such as being rotated in place, crimped inplace, or snapped in place using different structures other than thoseshown in the drawings of the present disclosure, etc.

In particular, it is contemplated that the opposed radial extensions maybe removed or eliminated from the collet insert, and that the colletinsert can be configured for downloading into the receiver open channelwith the protruding lateral ridges aligned with the receiver channel,and then rotated or twisted into position with the protruding lateralridges engaged within the upper shipping state groove and the openinsert channel coming into alignment with the open receiver channel. Theamount of rotation can be about 90 degrees. In some embodiments thecollet insert can be prevented from further rotation within the receiverby using crimps, a blocking tab or stop structure, and the like. It willbe appreciated that the “Twist-In-Place” embodiment of the collet insertcan still include downward tool deployment of the collet insert to thecapture/locking state position, with the opposed lateral ridges 158being snapped into the lower capture/locking state groove 122 followinga sliding biased engagement between the opposed lateral ridges 158 ofthe collet insert 150 and the discontinuous cylindrical surfaces 118 ofthe receiver central bore 114.

Additional details and disclosure regarding deployment tools or toolingfor preparing, assembling, and/or deploying bone screws and pivotal boneanchor assemblies or components thereof during spinal surgery, includinga receiver sub-assembly having an insert with “Twist-In-Place” anddownward tool deployment features similar to those described in thealternative above, can be found in co-pending Patent Cooperation Treaty(PCT) Application PCT/US2019/51190, filed Sep. 13, 2019, and claimingthe benefit of U.S. Provisional Application No. 62/731,059, filed Sep.13, 2018, with each of the above-referenced applications beingincorporated by reference in its entirety herein and for all purposes.

Illustrated in FIGS. 13-14 is the pressure ring 190 that is configuredto transfer a downwardly-directed force from the elongate rod 70 to thespherical outer surface 32 of the shank head 22. The pressure ring 190generally has a ring shaped body with an annular top surface 192, anannular bottom edge surface 198, and a substantially-cylindrical outersurface 194 that can be sized and shaped for slidable interferenceengagement with the interior sidewall surfaces of the collet pocket 164.For example, the diameter of the cylindrical outer surface 194 can beequal to or slightly greater than the inner diameter of the tubularsidewalls 162 and resilient collet fingers 168 that define the colletpocket 164, so as to provide a slight interference engagement when thepressure ring 190 is positioned in the upper portion of the colletpocket 164, with the slight interference engagement being sufficient tohold or maintain the pressure ring 190 within the collet pocket 164 inthe shipping state position. In one aspect the outer surface may furtherinclude an upper tapered or relief portion 195 above the cylindricalouter surface portion 194 that limits the interference engagement to anarrow cylindrical interference region spaced below the top surface 192of the pressure ring 190, and which can further facilitate the uploadingand positioning of the pressure ring into the collet portion 160 of thecollet insert 150.

The top surface 192 of the pressure ring 190 is configured to engage thebottom or lowermost or underside surface 74 of the elongate rod 70 whenthe elongate rod is positioned within the collet insert channel 156. Asshown in the drawings, the top surface 192 can be a symmetricalsubstantially-planar annular surface, having a symmetrical shape thatallows for uploading the pressure ring 190 into the collet pocket 164 inany rotational orientation. A central tool receiving aperture 199 isformed through the top surface 192 to allow passage of a driving tool toengage the shank head tool engagement structure 24 or drive socket thatis captured within the collet pocket 164, and which central aperture199, in one aspect, can be defined by a cylindrical inner surface 195that is smooth and non-threaded. As discussed below, outer edge portionsof the top surface 192 can abut the discontinuous downwardly-facing stopsurface 161 of the collet insert 150 when the pressure ring 190 isuploaded into the shipping state configuration within the collet insert150.

Extending between the cylindrical inner surface 195 and the annularbottom edge surface 198 of the pressure ring 190 is an inner or lower,downwardly-opening concave surface 196 that is configured to receive andmate with the spherical outer surface 32 of the shank head 22. The lowerconcave surface 196 can be textured, ridged, coated, and the like, toimprove the frictional engagement with the spherical outer surface 32.

It is foreseen that other shapes and configurations for the pressurering 190, different from those shown in the drawings while providing forsimilar interaction and functionality, are also possible and consideredto fall within the scope of the present disclosure. For example, it iscontemplated that alternative embodiments of the pressure ring can beslotted, can have a snap fitment with the collet insert, can have outerthreads that mate with the collet insert, can include an alignmentfeature or structure that engages with a complementary structure in thecollet insert, or can have a curved or channeled top surface that isalignable with the insert channel, and the like.

As described in more detail below, the pressure ring 190 is generallyuploaded into the expandable collet pocket 164 after the collet insert150 has been downloaded into its shipping state position, with theopposed lateral ridges 158 of the collet insert 150 engaged within theupper grooves 120 of the receiver 100. It is nevertheless foreseen thatthe pressure ring may be uploaded into the collet pocket prior topre-assembly, and then downloaded together with the collet insert intothe shipping state position.

With particular reference to FIGS. 15-18, the closure 50 comprises agenerally cylindrical closure body having a top surface 52, a bottomsurface 56, and an outer continuous guide and advancement structure 60formed into the outer side surface 54 of the closure body that operablyjoins with the guide and advancement structure 116 formed into theinterior face 110 of the receiver arms 104. In one aspect the guide andadvancement structures 60, 116 can be helically wound flanges withsplay-resisting or splay-controlling flange profiles for operablyguiding under rotation and advancing the closure structure 50 downwardbetween the arms 104 and having such a nature as to resist or controlthe splaying of the arms 104 when the closure structure 50 is advancedinto the receiver channel 106. In other aspects the guide andadvancement structures 60, 116 may take on a variety of alternativeforms, including but not limited to a buttress thread, a square thread,a reverse angle thread, or other thread like or non-thread likehelically wound advancement structure.

As shown in the drawings, in one aspect the bottom surface 56 of theclosure can include a downwardly-projecting central projection 58 forengaging and securing the elongate rod, and for controlling the closuretorque to thrust ratio. In other embodiments the bottom surface caninclude an annular projection, a point ring (i.e. an annular ringsurrounding a central point or projection), a recessed surfacesurrounded by a low outer ridge, and the like. In yet other embodimentsthe bottom surface 56 can be substantially planar across the extentthereof.

The top surface 52 of the closure 50 can further include a driving toolengagement structure, such as internal drive socket 66, which extendsdownward or inward into the body of the closure 50. The internal drivesocket 66 can be used for closure installation or removal. Similar tothe internal drive socket formed into the shank head, the internalsocket 66 of the illustrated closure 50 is an aperture formed in the topsurface 52, and in one aspect can be a multi-lobular or star-shapedaperture, such as those sold under the trademark TORX, or the like,having internal faces 68 designed to receiver to a multi-lobular orstar-shaped tool for rotating and driving the closure 50. It is foreseenthat such an internal tool engagement structure 66 may take a variety oftool-engaging forms and may include one or more apertures of variousshapes, such as a pair of spaced apart apertures or a hex shape designedto receive a hex tool (not shown) of an Allen wrench type. The seat orbase surface 67 of the drive feature 66 is disposed perpendicular to aclosure axis, with the drive feature 66 otherwise being coaxial with theaxis.

In another aspect of the present disclosure, a break-off extension (notshown) can be attached the upper end or top surface of the closure, andextend upwardly away therefrom to provide an external tool engagementstructure that can be used for rotatably advancing the closure downwardbetween the arms 104 of the receiver 100. In one aspect the break-offextension can be designed to allow the extension to break from theclosure at a preselected torque, for example, 60 to 140 inch pounds. Itis further foreseen that closures having other shapes, configurations,thread forms or non-threaded engagement alternatives, and the like, thatare different from those shown in the drawings while providing forsimilar interaction and functionality of the various components of thepivotal bone anchor assembly, are also possible and considered to fallwithin the scope of the present disclosure.

With reference to FIG. 19, the receiver 100, the collet insert 150, andthe pressure ring 190 form the components of a receiver sub-assembly 14,and are generally pre-assembled together at a factory setting thatincludes tooling for holding, alignment and manipulation of thecomponent pieces. In some circumstances, the shank is also assembledwith the receiver sub-assembly 14 at the factory. In other instances, itis desirable to first implant the shank, followed by addition of thepre-assembled receiver sub-assembly at the insertion point (see, e.g.,FIGS. 29-48). In this way, the surgeon may advantageously and moreeasily implant and manipulate a number of shanks along the patient'sspine, distract or compress the vertebrae with the shanks, and workaround the shank upper portions or shank heads without the cooperatingreceivers being in the way. In other instances, it is desirable for thesurgical staff to pre-assemble a shank of a desired size and/or variety(e.g., cannulated shank body, different thread patterns on the shankbody, and/or hydroxyapatite on the shank body), with the receiversub-assembly prior to implantation of the shank into a patient'svertebra. Allowing the surgeon to choose the appropriately sized, type,or treated shank advantageously reduces inventory requirements, thusreducing overall cost.

The pre-assembly of the receiver 100, the collet insert 150, and thepressure ring 190 components of FIG. 19 into a receiver sub-assembly 14is shown in FIGS. 20-28. With particular reference to FIGS. 20-21 and26, first the opposed radial extensions 180 of the collet insert 150 arealigned with the rod channel 106 of the receiver, and then the colletinsert 150 is dropped or driven downward into the central bore 114 ofthe receiver 100 (FIG. 20) until the opposed lateral ridges 158 orprojections become engaged within the receiver upper shipping stategrooves 120 (FIGS. 21, 26). In one aspect tooling (not shown) may beused to pinch inward the insert upright arms 154 as the collet insert150 is dropped downwardly into position, so as to allow the colletinsert lateral ridges 158 to pass downward through the guide andadvancement structure 116 of the receiver 100 without significantinterference between the parts. Alternatively, tooling (not shown) maybe used to press open the receiver arms 104 and expand the receiverchannel 106 as the collet insert 150 is dropped downwardly intoposition, also to allow the insert lateral ridges to pass downwardthrough the receiver guide and advancement structure.

With continued reference to FIG. 21, during the downloading of thecollet insert 150 to the shipping state position, the insert opposedradial extensions 180 can become slidably engaged by the upper opposingplanar surfaces 112 of the receiver upright arms 104 to prevent thecollet insert from rotating within the receiver axial bore 114. Inaddition, with the exterior projecting ridges 158 becoming engagedwithin the receiver upper shipping state grooves 120, the distal tipsections 170 of the resilient collet fingers 168 are suspended andcentralized within the upper expansion chamber portion 128 of thereceiver cavity 126.

With reference to FIGS. 22-23, the pressure ring 190 can now be uploadedthrough the receiver bottom opening 136 and into the collet insertdistal pocket opening 176, causing the collet fingers 168 to flexoutwardly and the distal pocket opening 176 to expand within theexpansion chamber 128 while the innermost edges 173 of the distal tipsections 170 slide against the cylindrical outer surface 194 of thepressure ring 190.

With reference to FIGS. 24-25, the pressure ring 190 can continue upwardthrough the collet pocket 164 until it reaches the shipping stateconfiguration, in which the annular top surface 192 of the pressure ring190 abuts the discontinuous downwardly-facing stop surface 161 of thecollet insert 150. In this position the top surface 192 of the pressurering 190 can also be substantially flush with the planar top edgesurfaces 184 of the radial extensions 180. In one aspect the enclosedpressure ring 150 can be pressed into a slight interference engagementin its position within the upper portion of the collet pocket 164, in alocation that is at least partially above the longitudinal slots 166and/or relief apertures 167 that define the resilient collet fingers168. With the top surface 192 of the pressure ring abutting thedownwardly-facing stop surface 161, the pre-assembly of the receiversub-assembly 14 is complete.

As shown in FIGS. 24-25 and 27, the receiver sub-assembly 14 is in ashipping state configuration in which the collet insert 150 is held in avertical position within the receiver central axial bore 114 andinhibited from vertical movement due to the overlapped (or overlapping)engagement of the opposed lateral ridges 158 being received within theupper shipping state grooves 120. Furthermore, the upper shipping stategrooves 120 are sized and shaped to prevent any upward movement of thecollet insert 150 relative to the receiver 100, while allowing fordownward movement or deployment of the collet insert 150 only withconsiderable direct force that may be provided by the appropriatetooling. As shown in FIG. 24, the collet insert is also held or‘clocked’ in angular position by the opposed radial extensions 180 thatare positioned between the upper opposing planar surfaces 112 of thereceiver upright arms 104. As noted above, the pressure insert 190 mayalso be held or secured within the upper continuous cylindrical portionof the collet pocket 164 with a slight interference engagement, or someother type of engagement, between the cylindrical outer surface 194 ofthe pressure ring 190 and the inner surface 163 of the tubular sidewall162. In one aspect the shipping state configuration shown in FIGS. 24-25and 27 may also be known as the collet insert/pressure ringpre-deployment configuration.

Furthermore, and with additional reference to FIG. 28, the distal tipsections 170 of the resilient collet fingers 168, acting as a retainer,will be suspended and centralized within the upper expansion chamberportion 128 of the receiver cavity 126 and spaced above the receiverbottom opening 136, in preparation for receiving the spherical head ofthe bone anchor. The outer partial spherical surfaces 174 of the distaltip sections 170 are also positioned vertically above the partialspherical interior seating surface 132 that is located just above thereceiver bottom opening 136. As discussed below, the inner diameter ofthe partial spherical interior seating surface 132 can be equal to orgreater than the outer diameter of the outer partial spherical surfaces174 of the distal tip sections 170, so that the distal tip sections (andresilient collet fingers 168) can be maintained in a neutral position orin a slightly expanded position when the collet insert 150 is in a lower“capture/locking state” position.

Illustrated in FIGS. 29-43 is the assembly or coupling of thepre-assembled receiver sub-assembly 14 of the pivotal bone anchorassembly 10 of the present disclosure to the head 22 of a shank or boneanchor 20. As shown in FIG. 29, the receiver sub-assembly 14 is firstpositioned above the shank head 22 with the receiver bottom opening 136generally aligned with the spherical outer surface 32 of the shank head22.

With reference to FIGS. 30-31, the receiver sub-assembly 14 is thendropped downward (or the shank 20 is moved upward, depending on theframe of reference of the reader) until the shank head 22 enters thebottom opening 136 and the upper portion of the spherical outer surface32 contacts the innermost edges 173 of the distal tip sections 170. Aspreviously described, the innermost edges 173 or chamfered surface 175of the distal tip sections 170 can be rounded or chamfered to facilitateslidable engagement with the spherical outer surface 32.

With reference to FIGS. 32-33, the receiver sub-assembly 14 continues tomove downward (or the shank 20 moves upward) as the upper portion of theshank head spherical outer surface 22 bears against the innermost edges173 of the distal tip sections 170, causing the collet fingers 168 toflex outward and the distal pocket opening 176 to expand within theupper expansion chamber portion 128 of the receiver cavity 126, untilthe distal pocket opening reaches maximum expansion.

With reference to FIGS. 34-35, the receiver sub-assembly 14 continues tomove downward (or the shank 20 moves upward) until the shank head 22reaches max push-through, in which the upper portion of the sphericalouter surface 32 abuts the lower concave surface 196 of the pressurering 190 and a center portion of the spherical outer surface 32 bearsagainst the inner surfaces 163 of the substantially cylindricalsidewalls 163 that define the collet pocket 164.

With reference to FIGS. 36-37, the receiver sub-assembly 14 is moved orpulled back upward (or the shank 20 downward) until the lower portion ofthe spherical outer surface 32 of the shank head 22 contacts theplurality of inner partial spherical surfaces 172 of the distal tipsections 170. In one aspect the collet fingers 168 can be slightlyexpanded compared to their nominal state so as to provide a lightfriction fit or head drag between the shank 20 and receiver 100, priorto the collet insert 150 being downwardly deployed within the receiver100. The shank head 22 is now lightly captured within the pocket 164 ofthe collet insert 150, but could still be removed from the receiversub-assembly 14 if the shank 20 were to be pulled forcefully downward,causing the resilient collet fingers 166 to expand and release the shankhead 22 from the collet pocket 164.

With reference to FIGS. 38-39, the collet insert 150, together with theenclosed pressure ring 190 and lightly captured shank head 22, can thenbe pushed downward with deployment tooling (not shown) that engages theplanar top edge surfaces 184 of the opposed radial extensions 180. Thepushing or deployment can include the application of considerable forceto the top of the collet insert tool engagement surfaces 184, so as topush the opposed lateral ridges 158 of the collet insert 150 downwardout of the upper shipping state grooves 20 of the receiver 100 and ontothe discontinuous cylindrical surface 118 of the central bore 114, wherethe lateral ridges 158 encounter an interference fit that resists thedownward motion. The force required to overcome this interference fitcan be about 200 pounds-force or greater, and is generally provided bythe deployment tooling. This action can temporarily cause theupwardly-projecting arms 154 of the collet insert 150 to flex inwardly,temporarily reducing the gap at the top of the collet insert channel156. With the collet insert 150 in this position, the elongate rod 70would not necessarily fit within the collet insert channel 156. Asdescribed above, the outer surface of the pressure ring 190 can have anupper tapered relief portion 193 that is tapered inwardly to provideroom for this inward flexing of the upright arms 154 of the colletinsert 150, so as to allow the lateral ridges 158 to become disengagedfrom the upper shipping state grooves 120 of the receiver 100. In analternative embodiment, the deployment tooling (not shown) can also orpreferably engage the upper tool engagement structure (e.g. recess 155)formed into the discontinuous upper cylindrical surface 153 of theintegral upright arms 154 extending above the collet portion of thecollet insert 150.

With reference to FIGS. 40-41, the collet insert 150 with the enclosedpressure ring 190 can continue to be pushed or deployed downward withthe deployment tooling until (a) the opposed lateral ridges 158 snapinto the lower “capture/locking state” grooves 122 of the receivercentral bore 114, (b) the partial spherical interior seating surface 132engages the plurality of outer partial spherical surfaces 174 of thedistal tip sections 170 to restrain further outward movement or flexingof the distal tip sections 170, and (c) the plurality of inner partialspherical surfaces 172 of the distal tip sections 170 more forcefullyengage the lower portion of the spherical outer surface 32 of the shankhead 22 to prevent the shank head 22 from exiting downward through thereceiver bottom opening 136. The shank head 22 is now fully capturedwithin the receiver sub-assembly 114 with the collet insert in thecapture/locking state position.

During the downward deployment of the collet insert 150 to thecapture/locking state position shown in FIGS. 40-41, the outer partialspherical surfaces 174 of the distal tip sections 170 may descendvertically through the receiver internal cavity 126 until engaging withand seating upon the partial spherical interior seating surface 132. Asnoted above, the inner diameter of the partial spherical interiorseating surface 132 can be equal to or slightly greater than the outerdiameter of the outer partial spherical surfaces 174 of the distal tipsections, so that distal tip sections 170 (and the resilient colletfingers 168) can be maintained in a neutral position or in a slightlyexpanded position when the collet insert 150 is in the lowercapture/locking state position.

In addition, it will be appreciated that the partial spherical interiorseating surface 132 of the receiver cavity 126, the outer partialspherical surfaces 174 of the distal tip sections 170, the inner partialspherical surfaces 172 of the distal tip sections 170, and the sphericalouter surface 32 of the shank head 20 can, in one aspect, define foursubstantially-concentric spherical surfaces (i.e. when their geometriccenters are located at substantially the same location along thereceiver longitudinal axis). Alternatively, it is also contemplated thatthe geometric centers of one or more of the spherical surfaces (e.g. thereceiver partial spherical seating surface) can be vertically offsetfrom the other geometric centers to facilitate the separation of thesurfaces during remobilization, as described in more detail below. It isfurther foreseen that other diameters and/or configurations for thepartial spherical surfaces and their geometric centers are alsopossible.

With reference to FIGS. 42-43 and 46, the enclosed pressure ring 190 cannow be individually pushed or deployed downwardly from its position inthe upper portion of the collet pocket 164 until the lower,downwardly-opening concave surface 196 of the pressure ring engages theupper portion of the spherical outer surface 32 of the shank head 22. Adownwardly-directed force sufficient to overcome the slight interferenceengagement between the cylindrical outer surface 194 of the pressurering 190 and the tubular sidewall inner surfaces 163 of the colletpocket 64 may be required. The downwardly-directed force can be directlyapplied with a tool or by the elongate rod positioned in the receiverand insert channels 106, 156 prior to deployment. In one aspect thecapture/locking state configuration shown in 42-43 and 46 may also beknown as the collet insert/pressure ring post-deployment configuration.

Optionally, once engaged with the shank head 22, the pressure ring 190may be further compressed downward onto the shank head 22 by adeployment tool, so as to apply an initial loading onto the sphericalouter surface 32 that is transferred downward to the partial sphericalseating surface 132 of the receiver cavity 126. This initial compressiveloading may be maintained by a frictional interference fit between thecylindrical outer surface 194 of the pressure ring 190 and the sidewallinner surfaces 163 of the collet pocket 164. In one aspect thecompressive loading may also be sufficient to establish, or furtherassure, a non-floppy friction fit that holds the position of thereceiver sub-assembly 14 relative to the shank head 22, while stillallowing for movement of the receiver sub-assembly 14 relative to thebone anchor 20 with an applied force. For example, the friction fit canallow for rotation of the receiver 100 around the shank head 22, with anapplied twisting force, so as to align the receiver channel 106 with thereceiver channels of one or more adjacent bone anchor assemblies. Thefriction fit can also allow for angulation of the receiver 100 relativethe shank head 22, with an applied moment force, also to align thereceiver channel 106 with the receiver channels of an adjacent boneanchor assembly.

Illustrated in FIGS. 44-45 and 47-48 is the pivotal bone anchor assembly10 as fully assembled and locked with the elongate rod 70 and closure50. For instance, after a desired alignment of the receiver sub-assembly14 to the bone anchor 20 has been achieved, the elongate rod 70 can beinstalled (i.e. reduced) into the collet insert channel 156 until thelowermost or underside surface 74 of the elongate rod 70 engages the topsurface 192 of the pressure ring 150. The closure 50 can then beinstalled into the upper portion of the receiver axial bore 114, inwhich the continuous guide and advancement structure 60 of the closurebody engages the discontinuous guide and advancement structure 116formed into the interior face 110 of the receiver upright arms 104. Theclosure 50 can be threaded downwardly until the bottom surface 56 or theprotrusion 58 of the closure 50 engages the top surface 72 of theelongate rod 70. Further rotation/torqueing of the closure 50 can thenbe used to drive the elongate rod 70 downward onto the pressure ring190, which in turn drives the shank head 22 and the distal tip sections170 of the collet insert 150 further downward into the partial sphericalseating surface 132 to achieve a final locking of the bone anchorassembly 10, in which the receiver sub-assembly 14 can no longer moverelative to the bone anchor 20.

In one aspect the elongate rod 70 does not push directly on the colletinsert 150 after downloading into the collet insert channel 156, as thetop surface 192 of the pressure ring 190 remains above the upper curvedsurfaces 182 of the opposed insert extensions 180 to establish a singleload path from the elongate rod 70 down into the receiver body 100 viathe pressure ring 190. Thus, the final locked state of the shank head 22can be provided from above by frictional engagement between thedownwardly-opening concave surface 196 of the pressure ring 190 and theupper portion of the spherical outer surface 32 of the shank head 22,and from below by frictional engagement between the plurality of innerpartial spherical surfaces 172 of the distal tip sections 170 and thelower portion of the spherical outer surface 32.

In yet another aspect of the disclosure, a closure break-off extension(not shown) can be configured to shear away from the top surface or end52 of the closure body at a pre-determined torque value, therebyensuring that the pivotal bone anchor assembly 10 is fully locked at aconsistent pre-determined torque value.

Furthermore, it will be appreciated by one of skill in the art that theinterface between the receiver cavity partial spherical seating surface132 and the plurality of outer partial spherical surfaces 174 of thedistal tip sections 170 can determine the strength, or pull-outresistance, of the fully locked pivotal bone anchor assembly 10. Forexample, and with reference back to FIG. 46, the distal tip sections 170of the collet insert 150 are generally configured to transfer load fromthe shank head 22 to the receiver base 134. Relative motion between thedistal tip sections 170 and the receiver base 134 is limited by frictionand interference between the outer surfaces 174 of the distal tipsections 170 and the partial spherical seating surface 132 of thereceiver cavity 126. Assuming that relative motion between the distaltip sections 170 and the receiver base 134 is restricted orsubstantially prevented, pull-out resistance of the shank or bone anchor20 is provided by a plurality of shear walls in the collet fingers168/distal tip sections 170 that start at the major diameter of theshank head 22 and terminate at the bottom surface 178 of the distal tipsections 170.

Among others, one useful aspect of the fully-assembled pivotal boneanchor assembly 10 disclosed above is that bone anchor assembly 10 canbe re-mobilized relative to the head 22 of the bone anchor 20 simply byremoving or loosening the closure. For example, and with reference toFIGS. 49-51, the closure and elongate can be removed so as to remobilizethe pivotal bone anchor assembly 10 relative to the shank head 22.Although the bone anchor assembly 10 is shown in the drawings with theclosure and elongate rod being completely removed, remobilization can beaccomplished simply by loosening the closure while leaving both theclosure and elongate rod in place. Loosening the closure removes thedownward force applied to the pressure ring 190 through the elongaterod, thereby reducing the frictional engagement on the upper and lowerportions of the spherical outer surface 32 of the shank head 22. Withthe reduction of the frictional engagement on the upper and lowerportions of the spherical outer surface, the receiver sub-assembly 14becomes free again to rotate relative to the shank head 22.

As previously described, the partial spherical profile of the receivercavity seating surface 132 can be substantially concentric with each ofthe partial spherical profiles of the outer surfaces 174 and innersurfaces 172 of the distal tip sections 170, and with the sphericalprofile of the shank head 22. This design reduces the likelihood forinadvertently creating a permanently locked engagement between thedistal tip sections 170 of the collet insert 150 and the receiver cavityseating surface 132 when fully locking the pivotal bone anchor assembly10, as described and illustrated above. For example, using a partialspherical profile for the seating surface 132 of the receiver cavity126, rather than a conical or tapered profile, better distributes thefriction forces across the seating surface 132, better centers thecollet fingers 168 around the circumference of the receiver cavityseating surface 132 to avoid cocking/misalignment of the collet insert150 within the receiver cavity 126, avoids creating a concentrated lineof contact that may cause localized deformation and bonding between thetwo surfaces 132, 174; and avoids a tapered locking engagement betweenthe collet insert 150 and the receiver 100. As noted above, thegeometric center of the partial spherical profile of the receiver cavityseating surface 132 can also be vertically offset or displaced slightlyfrom the geometric centers of the other three spherical profiles. It iscontemplated that this vertical displacement can operate to re-directthe normal force to twist the upper portions of the distal tip sections170 toward or away from the partial spherical seating surface 132 of thereceiver cavity 126.

Illustrated in FIGS. 52-59 is the disassembly and removal of thereceiver sub-assembly 14 of the pivotal bone anchor assembly 10 from thehead 22 of the shank or bone anchor 20. As shown first in FIG. 52, afterthe removal of the closure and the elongate rod from the receiversub-assembly 14, a disassembly tool 80 can be downwardly introduced intothe open channel 106 of the receiver 100 and engaged with the colletinsert 150. The disassembly tool 80 includes a center portion 82comprising two downwardly-extending prongs 84, with each prong having anoutwardly-facing hook portion 86 that is sized and shaped to engage withthe upper tool engagement structures or recesses 155 formed into thediscontinuous upper cylindrical surface 153 of the insert arms 154 ofthe collet insert 150. The prongs 84 may be configured to flex inwardlytoward each other, with the lower tip 88 of each prong 84 including atapered surface 89 that first contacts the top edge of an insert uprightarm 154 when introduced into the open channel 106 of the receiver 100.This initial contact can cause the prongs 84 to flex inwardly towardeach other, after which the outwardly-facing hook portions 86 ridedownwardly along the discontinuous cylindrical surfaces 153 of theinsert arms 154 until they snap into the upper tool engagement recesses155 (FIGS. 53-54). Alternatively, the prongs 84 of the disassembly tool80 may be orientated to align with the open channel 106 of the receiver100 and the open channel 156 of the collet insert 150 before beingpositioned downwardly within the insert channel 156, and then rotatedabout the receiver longitudinal axis until the hook portions 86 engagewith the upper tool engagement recesses 153.

Once the hook portions 86 of the disassembly tool 80 are engaged withinthe upper tool engagement recesses 153, as shown in FIGS. 53-54, thecenter portion 82 of the disassembly tool 80 is withdrawn upward to pullthe opposed lateral ridges 158 of the collet insert 150 from the lowercapture/locking state grooves 122 to the upper shipping state grooves120, as shown in FIGS. 55-56. In practice, the disassembly tool 80 canfurther include an outer portion (not shown) that engages with andpushes downwardly on the receiver 100 while the center portion 82 iswithdrawn upwardly. This can include the application of considerableforce between the disassembly tool 80 and the receiver 100 to pull theopposed lateral ridges 158 upward out of the lower grooves 122 and ontothe discontinuous cylindrical surface 118 of the receiver central bore114. For example, in one aspect the force required to overcome thisengagement can be about 400 pounds-force or greater, generally providedby the counter-directional movement between the center portion 82 andouter portion of the disassembly tool 80. In situations where theposition of an implanted bone anchor 20 is fixed, this causes thereceiver 100 with its lower capture/locking state grooves 122 and uppershipping state grooves 120 to displace downwardly relative to the shankhead 22, rather than the collet insert 150 to displace upwardly. It willbe appreciated that the application of force between the disassemblytool 80 and the receiver 100, provided by the counter-directionalmovement between the center portion 82 and outer portion (not shown) ofthe disassembly tool 80, can substantially balance the load across thereceiver 100 so as to reduce or substantially eliminate the transfer ofany disassembly loads or forces to the shank head 22.

With reference to FIGS. 57-58, once the opposed lateral ridges 158 ofthe collet insert 150 are positioned within the upper shipping stategrooves 120, the entire receiver sub-assembly 14 can then be pulledupward off the bone anchor or shank 20 by the disassembly tool 80 havinghook portions 86 that are still engaged within the tool engagementrecesses 155 of the collet insert 150, causing the collet fingers 168 toflex outward and the distal pocket opening 176 to expand within theupper expansion chamber 128 of the receiver cavity 126, until the distalpocket opening 176 expands sufficiently to allow passage of the shankhead. The disassembly tool 80 can be used to continue pulling thereceiver sub-assembly 14 upward off the bone anchor 20 until the shankhead 22 exits the bottom opening 136 of the receiver 100, as shown inFIG. 59. After removal of the receiver sub-assembly 14 from the shankhead 22, in one aspect the disassembly tool 80 can be disengaged fromthe receiver sub-assembly 14 by rotating the disassembly tool 80 aboutthe receiver longitudinal axis until the hook portions 86 slide out fromthe tool engagement recesses 155 (see FIG. 59).

It is foreseen that other shapes and configurations for the disassemblytool 80, the receiver 100 and the collet insert 150, different fromthose shown in the drawings while providing for similar interaction andfunctionality for disassembling the pivotal bone anchor assembly, arealso possible and considered to fall within the scope of the presentdisclosure. For example, it is contemplated that the disassembly tool 80can access the collet insert 150 by other routes, such as throughapertures in the upright arms 104 of the receiver 100, and the like.

With reference to FIGS. 60-63, illustrated therein is anotherrepresentative embodiment 200 of the pivotal bone anchor assembly thatis substantially similar to the pivotal bone anchor assembly 10described above, except for modifications to the interface between thepartial spherical seating surface 214 of the receiver cavity 212, and tothe outer partial spherical surfaces 224 of the distal tip sections 222.In particular, the partial spherical seating surface 214 of the receiver210 can be modified to include an inwardly-projecting ridge 216 having ahorizontal top surface 217. In addition, the outer partial sphericalsurfaces 224 of the distal tip sections 222 can be modified to include acomplementary notch 226 that is sized and shaped to receive the ridge216 in the capture/locking state position, as shown in FIG. 63.

It is contemplated that the above-referenced modifications, which serveto establish a seating interface with a ridged surface, may modify orimprove the resistance to pull-out of the shank head 22 from thereceiver sub-assembly 204 during assembly, loading, and use. Forinstance, and similar to the pull-out analysis described above, theinterface between the receiver partial spherical seating surface 214with the inwardly-projecting ridge 216 and the plurality of outerpartial spherical surfaces 224 of the distal tip sections 222 candetermine the strength, or pull-out resistance, of the fully lockedpivotal bone anchor assembly 100. The distal tip sections 222 of thecollet insert 220 are configured to transfer load from the shank head 22to the receiver base 211. Relative motion between the distal tipsections 222 and the receiver base 211 is limited by friction and/orinterference between the notched outer surfaces 224 of the distal tipsections 222 and the ridged partial spherical seating surface 214 of thereceiver cavity 212. In addition, the downward-facing horizontal surface227 of the notch 226 engages with the mating upward-facing horizontalsurface 217 of the ridge 216 to provide a positive stop for distal tippull out relative to the receiver 210, as well as an indexed singlelocation for the collet insert 220 relative to the receiver 210.Assuming that relative motion between the distal tip sections 222 andthe receiver base 211 is restricted or substantially prevented, pull-outresistance of the shank 20 is provided by a plurality of shear walls inthe collet fingers 221 and distal tip sections 222 that start at themajor diameter of the shank head 222 and terminate at the bottom surface228 of the distal tip sections 222.

With reference to FIGS. 64-67, illustrated therein is yet anotherrepresentative embodiment 250 of the pivotal bone anchor assembly thatis also substantially similar to the pivotal bone anchor assembly 10described above, except for modifications to the interface between thepartial spherical seating surface 264 of the receiver cavity 262, and tothe outer partial spherical surfaces 274 of the distal tip sections 272.In particular, the partial spherical seating surface 264 of the receiver260 can be modified to include a horizontal, upwardly-facing steppedsurface 266 at the lower end thereof. In addition, the distal tipsections 272 of the collet insert 270 can be shortened so that, when thecollet insert 270 is downwardly deployed into the capture/locking stateposition, the bottom surfaces 278 of the distal tip sections 272simultaneously engage the upwardly-facing stepped surface 266 while theouter partial spherical surfaces 274 of the distal tip sections 222engage the partial spherical seating surface 264 of the receiver cavity262.

It is contemplated that the above-referenced modifications, which serveto establish a seating interface with a stepped surface, may improve theresistance to pull-out of the shank head 22 from the receiversub-assembly 254 during assembly, loading, and use. For instance, andsimilar to the pull-out analyses described above, the interface betweenthe partial spherical seating surface 264 with the upwardly-facingstepped surface 266 of the receiver 260 and the plurality of outerpartial spherical surfaces 274 and bottom surfaces 278 of the shorteneddistal tip sections 270 can determine the strength, or pull-outresistance, of the fully locked pivotal bone anchor assembly 250. Thedistal tip sections 272 of the collet insert 270 are configured totransfer load from the shank head 22 to the receiver base 261. Relativemotion between the distal tip sections 272 and the receiver base 261 islimited by friction and/or interference between the outer surfaces 274and bottom surfaces 278 of the distal tip sections 272 and the partialspherical seating surface 264 and stepped surfaces 266 of the receivercavity 262. In addition, the horizontal downward-facing bottom surfaces278 of the shortened distal tip sections 272 engage with the matinghorizontal upward-facing stepped surface 266 to provide a positive stopfor distal tip pull out relative to the receiver 260, as well as anindexed single location for the collet insert 270 relative to thereceiver 260. Assuming that relative motion between the distal tipsections 272 and the receiver base 261 is restricted or substantiallyprevented, pull-out resistance of the shank 20 is provided by aplurality of shear walls in the collet fingers 271 and distal tipsections 272 that start at the major diameter of the shank head 222 andterminate at the bottom surface 278 of the distal tip sections 272.

With reference to FIGS. 68-74, illustrated therein is yet anotherrepresentative embodiment 300 of the pivotal bone anchor assembly thatis also substantially similar to the pivotal bone anchor assembly 10described above, except for modifications to the interface between thepartial spherical seating surface 314 of the receiver cavity 312 and theouter partial spherical surfaces 324 of the distal tip sections 322. Inparticular, the partial spherical seating surface 314 can be modified toinclude a circumferential expansion ring slot 316 that is sized andshaped to receive a separate expansion ring 330. The expansion ring 330can be uploaded separately into the receiver cavity 312 prior to theuploading of the shank head 22. The expansion ring slot 316 issufficiently deep to allow the expansion ring 330 to expand outward toallow passage of the shank head 22 during uploading, and then to closeback around the lower portion of the spherical outer surface 32 belowthe hemisphere plane. In addition, the distal tip sections 322 of thecollet insert 320 can be shortened so that, when the collet insert 320is downwardly deployed into the capture/locking state position, thebottom surfaces 328 of the distal tip sections 322 simultaneously engagethe top surface 332 of the expansion ring 330 while the outer partialspherical surfaces 324 of the distal tip sections 322 engage the partialspherical seating surface 314 that is located above the circumferentialexpansion ring slot 316.

It is contemplated that the above-referenced modifications, which serveto establish a seating interface with expansion ring support, mayimprove the resistance to pull-out of the shank head 22 from thereceiver sub-assembly 304 during assembly, loading, and use. Forinstance, and similar to the pull-out analyses described above, theinterface between the partial spherical seating surface 314 and theexpansion ring 330 and the plurality of outer partial spherical surfaces324 of the distal tip sections 322 can determine the strength, orpull-out resistance of the fully locked pivotal bone anchor assembly300. The distal tip sections 322 of the collet insert 320 are configuredto transfer load from the shank head 22 to the receiver base 311.Relative motion between the distal tip sections 322 and the receiverbase 311 is limited by friction and interference between the outer andbottom surfaces of the distal tip sections 322 and the partial sphericalseating surface 314 of the receiver cavity 312 and the expansion ring300. In addition, the horizontal downward-facing bottom surfaces 328 ofthe shortened distal tip sections 322 engage with the mating horizontalupward-facing top surface 332 of the expansion ring 330 to provide apositive stop for distal tip pull out relative to the receiver 310, aswell as an indexed single location for the collet insert 320 relative tothe receiver 310. Assuming that relative motion between the distal tipsections 322 and the receiver base 311/expansion ring 330 is restrictedor substantially prevented, pull-out resistance of the shank 22 isprovided by a plurality of shear walls in the collet fingers 321 anddistal tip sections 322 that start at the major diameter of the shankhead 22 and terminate at the bottom surface 328 of the distal tipsections 322.

With reference to FIGS. 75-81, illustrated therein is yet anotherrepresentative embodiment 350 of the pivotal bone anchor assembly thatis also substantially similar to the pivotal bone anchor assembly 10described above, except for modifications to the interface between thepartial spherical seating surface 364 of the receiver cavity 362 and theouter partial spherical surfaces 374 of the distal tip sections 372. Inparticular, the partial spherical seating surface 364 can be modified toinclude a circumferential expansion ring slot 366 that is sized andshaped to receive a separate expansion ring 380, which is subsequentlyrestrained by tab extensions 373 projecting from the collet insert 370.The expansion ring 380 can be uploaded separately into the receivercavity 362 prior to the uploading of the shank head 22. The expansionring slot 366 is sufficiently deep to allow the expansion ring 380 toexpand outward to allow passage of the shank head 22. The distal tipsections 372 of the collet insert 370 can be shorted so that, when thecollet insert 370 is downwardly deployed into the capture/locking stateposition, the bottom surfaces 378 of the distal tip sections 372simultaneously engage the top surface 382 of the expansion ring 380while the outer partial spherical surfaces 374 of the distal tipsections 372 engage the receiver partial spherical seating surface 364.

As can be seen in the drawings, the distal tip sections 372 of thecollet insert 370 can be further modified to include tab extensions 373that project radially outward from distal tip sections 372 of aplurality of collet fingers 371. In one embodiment, three of six colletfingers 371 can include tab extensions 373 while the remaining three canhave outer partial spherical surfaces 374. The upper expansion chamberand the conical transition surface portions of the receiver cavity 362can also be further modified to include a plurality of vertical recesses368 that are sized and shaped to receive the plurality of tab extensions373 projecting radially from the distal tip sections 372 of the colletinsert 370. When the collet insert 370 is downwardly deployed into thecapture/locking state position, the tab extensions 373 can slide behindthe expansion ring 380 to prevent the outward deflection of theexpansion ring 380 into the expansion ring slot 366 during loading ofthe pivotal bone anchor 350. The tab extensions 373 can prevent outwardexpansion of the expansion ring 380 back into its expansion ring slot366 to better restrict the relative motion between the distal tipsections 370 and the receiver base 361 and expansion ring 380.

It is contemplated that the above-referenced modifications, which serveto establish a seating interface with constrained expansion ringsupport, may improve the resistance to pull-out of the shank head 22from the receiver sub-assembly 354 during assembly, loading, and use.For instance, and similar to the pull-out analyses described above, theinterface between the partial spherical seating surface 364 and theexpansion ring 380 and the plurality of outer partial spherical surfaces374 of the distal tip sections 372 can determine the strength, orpull-out resistance, of the fully locked pivotal bone anchor assembly350. The distal tip sections 372 of the collet insert 370 are configuredto transfer load from the shank head 22 to the receiver base 361.Relative motion between the distal tip sections 372 and the receiverbase 361 is limited by friction and interference between the outersurfaces 374 and bottom surfaces 378 of the distal tip sections 372 andthe partial spherical seating surface 364 of the receiver cavity 362 andexpansion ring 380. In addition, the horizontal downward-facing bottomsurfaces 378 of the shortened distal tip sections 372 engage with themating horizontal upward-facing top surface 382 of the expansion ring380 to provide a positive stop for distal tip pull out relative to thereceiver 360, as well as an indexed single location for the colletinsert 370 relative to the receiver 360. Assuming that relative motionbetween the distal tip sections 372 and the receiver base 361 and theexpansion ring 380 is restricted or substantially prevented, pull-outresistance of the shank 20 is provided by a plurality of shear walls inthe collet fingers 371 and distal tip sections 372 that start at themajor diameter of the shank head 22 and terminate at the bottom surface378 of the distal tip sections 372.

Illustrated in FIGS. 82-84 is yet another representative embodiment 400of a pivotal bone anchor apparatus or assembly in which the elongaterods and receivers have been replaced with housings 410 that provide foradjacent level connection. For example, the housings 410 of the pivotalbone anchor assemblies 400 can replace the receiver 100 discussed abovewith respect to FIGS. 1-59, with the housings 410 containing internalcomponents, such as a modified collet insert 420 and an enclosedpressure ring 430, that are similar in function to the collet insert andenclosed pressure ring described above as residing in the receiver 100shown in FIGS. 1-99.

As shown in FIG. 82, in one aspect the housings 410 of the pivotal boneanchor assembly can be separated into a male housing 412 having a malecord or projection 414 that is received in pivotal arrangement within afemale receptacle 418 of a female housing 416 immediately adjacent themale housing 412.

The housing 410 of FIGS. 83-84 further illustrates the separate colletinsert 420 that has been modified to remove the upwardly projecting armstructures that define an insert channel, while still includingstructures that can provide for the downward deployment of the colletinsert 420 within the housing 410 to a capture/locking state positionaround the shank head 22, prior to the installation of the closure 440.For example, the collet insert 420 can include insert ridges that snapinto lower capture/locking receiver grooves, the partial sphericalseating surface of the receiver cavity can engage the plurality of outerpartial spherical surfaces of the distal tip sections to restrainfurther outward movement for flexing of the distal tip sections, and theplurality of inner partial spherical surfaces of the distal tip sectionsmore forcefully engage the lower portion of the spherical outer surfaceof the shank head 22 to prevent the shank head from exiting downwardthrough the receiver bottom opening.

Also as described above, the pressure ring 430 is subsequentlydownwardly deployable from its position in the upper portion of thecollet pocket until the upwardly-concave partially spherical bottomsurface of the load ring engages the upper portion of the shank headspherical surface. In one aspect the deployment of the pressure ring issufficient to establish, or further assure, a non-floppy friction fitthat holds the position of the receiver sub-assembly relative to theshank head 22, while still allowing for movement of the receiversub-assembly relative to the bone anchor 20 with an applied force.

With housings 410 so equipped with these internals, each housing 410 isalso able to couple with the above-described shank heads 22, asgenerally outlined above with respect to FIGS. 1-59. The receivers andhousings thus may be considered different versions of a structuralenvelope that contains complimentary versions a collet insert and anenclosed pressure ring.

As indicated above, the invention has been described herein in terms ofpreferred embodiments and methodologies considered by the inventor torepresent the best mode of carrying out the invention. It will beunderstood by the skilled artisan, however, that a wide range ofadditions, deletions, and modifications, both subtle and gross, may bemade to the illustrated and exemplary embodiments of the pivotal boneanchor assembly without departing from the spirit and scope of theinvention. These and other revisions might be made by those of skill inthe art without departing from the spirit and scope of the inventionthat is constrained only by the following claims.

What is claimed is:
 1. A pivotal bone anchor assembly for securing anelongate rod to a bone of a patient via a closure, the pivotal boneanchor assembly comprising: a shank having a longitudinal axis, a headportion with a partial spherical shape defining a hemisphere plane at amaximum width perpendicular to the longitudinal axis, a spherical outersurface having a single common radius extending above and below thehemisphere plane, and an anchor portion opposite the head portionconfigured for fixation to the bone; a receiver comprising a basedefining an internal cavity in communication with a bottom of thereceiver through a bottom opening, an upper portion defining a firstchannel configured for receiving the elongate rod, and a central borecentered around a vertical centerline axis extending upward from thebottom opening through the internal cavity and the first channel to topsurfaces of the receiver, the internal cavity having an upper expansionportion and a lower seating surface proximate the bottom opening, thecentral bore including at least one pair of internal recesses havingdownwardly-facing upper surfaces; a collet insert configured for toploading into the central bore of the receiver, the collet insertcomprising: a collet portion having a tubular sidewall defining a colletpocket configured for receiving the head portion of the shank, thetubular sidewall having a plurality of longitudinal slots formedtherethrough to define a plurality of downwardly-extending resilientcollet fingers, and a plurality of distal tip sections at lower ends ofthe collet fingers, the distal tip sections defining a collet pocketopening configured for expansion within the central bore; and a pair ofcollet insert arms extending upwardly from the collet portion to definea second channel configured for positioning within the first channel andfor receiving the elongate rod, each of the pair of collet insert armshaving an outer protrusion configured for positioning into one of the atleast one pair of internal recesses and engageable with adownwardly-facing upper surface; and a pressure ring uploadable into thecollet pocket through the collet pocket opening before the head portionof the shank, the pressure ring having an upper surface configured toengage the elongate rod, a concave lower surface configured to engagethe spherical outer surface of the head portion, the pressure ring beingconfigured for non-overlapping engagement with the collet insert whenthe pivotal bone anchor assembly is in a locked configuration, whereinthe head portion of the shank is uploadable into the collet pocketthrough both the bottom opening of the receiver and the collet pocketopening of the collet insert when the collet insert and pressure ringare secured in a first position within the central bore of the receiverso as to be initially inhibited from axial movement with respect to thereceiver, and wherein the collet insert, the pressure ring, and the headportion of the shank are together downwardly deployable to a secondposition within the central bore of the receiver, in which outersurfaces of the plurality of distal tip sections are engageable with thelower seating surface of the internal cavity and inner partial sphericalsurfaces of the plurality of distal tip sections are engageable with thespherical outer surface of the head portion, so as to secure the headportion of the shank within the collet pocket with the shank extendingdownwardly through the bottom opening of the receiver.
 2. The pivotalbone anchor assembly of claim 1, wherein the at least one pair ofinternal recesses further comprises: a pair of upper shipping stateinternal recesses configured for receiving the pair of outer protrusionsto secure the collet insert in the first position; and a pair of lowerlocking state internal recesses configured for receiving the pair ofouter protrusions to secure the collet insert in the second position. 3.The pivotal bone anchor assembly of claim 1, wherein the plurality ofdistal tip sections at the lower ends of the collet fingers furthercomprises a plurality of enlarged distal tip sections having a thicknessgreater than a thickness of the tubular sidewall defining the colletpocket.
 4. The pivotal bone anchor assembly of claim 1, wherein thepressure ring is uploadable into the collet pocket after the colletinsert has been downloaded into the first position.
 5. The pivotal boneanchor assembly of claim 1, wherein the pressure ring is configured toengage an upper internal engagement surface of the collet pocket with aninterference fit when the collet insert and pressure ring are in thefirst position.
 6. The pivotal bone anchor assembly of claim 1, whereinafter the collet insert, the pressure ring, and the head portion of theshank are together downwardly deployed into the second position, thepressure ring is further downwardly deployable within the collet insertinto a locking state position.
 7. The pivotal bone anchor assembly ofclaim 6, wherein the pressure ring is downwardly deployable into thelocking state position with one of a removable deployment tool and theelongate rod being urged downward within the first and second channelsby the closure.
 8. The pivotal bone anchor assembly of claim 6, whereinan application of pressure to the upper surface of the pressure ringwhen the pressure ring is in the locking state position is configured tocause the concave lower surface of the pressure ring to engage againstthe spherical outer surface of the head portion of the shank andrestrict further motion of the shank relative to the receiver.
 9. Thepivotal bone anchor assembly of claim 8, wherein a release of thepressure to the upper surface of the pressure ring is configured torelease the engagement between the concave lower surface of the pressurering and the spherical outer surface of the head portion of the shank toremobilize the shank relative to the receiver.
 10. The pivotal boneanchor assembly of claim 1, wherein the distal tip sections of theresilient collet fingers are stabilized and centralized within theexpansion portion of the internal cavity when the collet insert in thefirst position.
 11. The pivotal bone anchor assembly of claim 1, whereinan inner diameter of the seating surface of the internal cavity is equalto or greater than an outer diameter of outer partial spherical surfacesformed on the distal tip sections, so that distal tip sections andresilient collet fingers are maintained in a neutral position or in aslightly expanded position when the collet insert is in the secondposition.
 12. The pivotal bone anchor assembly of claim 1, furthercomprising a pair of opposed radial extensions extending radiallyoutward from the collet portion of the collet insert and configured toengage with inner surfaces of the first channel to restrict rotation ofthe collet insert relative to the receiver.
 13. The pivotal bone anchorassembly of claim 1 and further comprising the elongate rod and theclosure, wherein the closure is configured for positioning entirelywithin the central bore of the receiver above the elongate rod and inengagement with a closure mating structure formed therein so as to applya downward pressure to a top of the elongate rod and secure the elongaterod to the bone of the patient.
 14. The pivotal bone anchor assembly ofclaim 13, wherein the collet insert further comprises a pair of oppositeradial extensions extending radially outward from the collet insert inthe direction of the channel of the receiver so as to maintain analignment of the collet insert between the receiver arms.
 15. Thepivotal bone anchor assembly of claim 14, further comprising lateralridges projecting radially outward from outer side surfaces of thecollet insert, and wherein the central bore of the receiver furthercomprises: upper grooves configured for receiving the lateral ridges tosecure the collet insert in the first position; and lower groovesconfigured for receiving the lateral ridges to secure the collet insertin the second position.
 16. The pivotal bone anchor assembly of claim15, wherein the collet insert is configured to be downloaded into thecentral bore of the receiver with the lateral ridges angularly alignedwith the channel until the lateral ridges become vertically aligned withthe upper grooves, and then rotated about the vertical centerline axisof the receiver until the lateral ridges are received in the uppergrooves in the first position.
 17. The pivotal bone anchor assembly ofclaim 16, wherein the rotation of the collet insert about the verticalcenterline axis is limited to about 90 degrees by a stop structure. 18.A pivotal bone anchor assembly for securing an elongate rod to a bone ofa patient via a closure, the pivotal bone anchor assembly comprising: ashank having a longitudinal axis, a head portion with a partialspherical shape, and an anchor portion opposite the head configured forfixation to the bone; a receiver comprising a base defining an internalcavity in communication with a bottom of the receiver through a bottomopening, a pair of receiver arms extending upwardly from the base todefine a channel for receiving the elongate rod, and a central borecentered around a vertical centerline axis, the central bore extendingupward from the bottom opening through the internal cavity and thechannel to top surfaces of the receiver arms; a collet insert toploadable into a first position within the central bore of the receiverand having a collet pocket configured for expansion within the centralbore so as to receive the head portion of the shank; and a pressure ringuploadable into the collet pocket before the head portion of the shankand having a top surface configured to engage the elongate rod, thepressure ring having a non-overlapping engagement with the collet insertin a locked orientation, wherein after receiving the head portion of theshank within the collet pocket, the collet insert, pressure ring, andshank are downwardly deployable into a second position within thecentral bore of the receiver to capture the head portion of the shank inthe assembly, with the pressure ring being operable to transfer pressurefrom the elongate rod positioned in the channel to the head portion ofthe shank to lock an angular position of the shank relative to thereceiver.
 19. The pivotal bone anchor assembly of claim 18, whereinafter the collet insert, the pressure ring, and the head portion of theshank are together downwardly deployed into the second position, thepressure ring is further downwardly deployable within the collet insertinto a locking state position to transfer the pressure from the elongaterod to the head portion of the shank.
 20. The pivotal bone anchorassembly of claim 19, wherein the collet pocket includes an upperinternal engagement surface configured to engage an outer surface of thepressure ring with a non-overlapping interference fit prior to thefurther downward deployment of the pressure ring into the locking stateposition.
 21. The pivotal bone anchor assembly of claim 18, wherein anapplication of pressure to the top surface of the pressure ring causes acurvate lower surface of the pressure ring to engage against the headportion of the shank and restrict further motion of the shank relativeto the receiver.
 22. The pivotal bone anchor assembly of claim 21,wherein a release of the pressure to the top surface of the pressurering is configured to release the engagement between the curvate lowersurface of the pressure ring and the head portion of the shank toremobilize the shank relative to the receiver.
 23. The pivotal boneanchor assembly of claim 18 and further comprising the elongate rod andthe closure, wherein the closure is configured for positioning entirelywithin the central bore of the receiver above the elongate rod and inengagement with a closure mating structure formed therein so as to applya downward pressure to a top of the elongate rod and secure the elongaterod to the bone of the patient.